STUDY OF MULTICOMPONENT SYSTEMS CONTAINING NITRILO-TRIMETHYLENE PHOSPHONIC (NTMP) ACID AS INHIBITORS FOR THE PROTECTION OF METALS IN NEUTRAL AQUEOUS-MEDIA

The inhibitor mixtures studied contain nitrilo-trimethylene phosphonic acid, oxalic acid or phthalic acid anhydride and zinc sulfate. On the basis of the measurement of the differential electric double-layer capacity using the bridge method the thermodynamic characteristics of the adsorption of the compounds studied and their mixtures on the surface of armco iron have been determined in aqueous potassium fluoride solutions. The best inhibitor mixture was then used as the starting material for optimizing the composition ratios. Using gravimetric techniques the influence of this mixture on the rate of corrosion of steel ST3S in simulated industrial water of variable chemical composition and in water being chlorinated. In addition the influence of this mixture on the rate of corrosion of copper (Cu 99,9 E), brass (CuZn 37), zinc (97.5) and aluminum alloy (AlCu4Mg1) has been studied as well and considerable decrease of the corrosion rate by the inhibitor mixtures has been established. Nitrilo-trimethylene phosphonic acid, in combination with phthalic acid anhydride and zinc ions can therefore be considered as a perspective inhibitor for the corrosion protection of industrial cooling and heating water installations.